The table ids is not correctly updated by zabbix-server
So that we have the auto-increment column "eventid" from the table "events" equal or greater than the corresponding "nextid" from the table "ids".
the sql code below shows the problem and how to manually solve it (we have put a cron doing that each minute).
The problem is blocking when adding a new host with a template, or when linking a template to an existing host (we obtain a mysql problem saying : "Duplicate Entry in key 1 of table events").

mysql> select max(eventid) from events; select * from ids where table_name='events'; update ids set nextid=((select max(eventid) from events) + 1 ) where table_name='events'; select max(eventid) from events; select * from ids where table_name='events';
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select max(eventid) from events
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1 row in set (0.00 sec)

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select * from ids where table_name='events'
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1 row in set (0.00 sec)

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update ids set nextid=((select max(eventid) from events) + 1 ) where table_name='events'
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Query OK, 1 row affected (0.03 sec)
Rows matched: 1 Changed: 1 Warnings: 0

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select max(eventid) from events
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1 row in set (0.00 sec)

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select * from ids where table_name='events'
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1 row in set (0.00 sec)